Mpxj

* Improve support for reading MPX files generated by SureTrak

* Fix WBS and Activity ordering for tasks from Primavera.

* Strip unescaped control characters from JSON output.

* For schedules imported from Primavera ensure tasks representing activities are ordered by Activity ID within the WBS to match Primavera.

* Avoid NPE when writing MSPDI files with timephased data (contributed by Bruno Gasnier)
* Improve resource assignment constructor (based on a contribution by Bruno Gasnier)
* Improve MPX French translations (contributed by Bruno Gasnier)
* Add calendar specific minutes per day, week, month, and year (based on a contribution by Bruno Gasnier)
* Add support for reading and writing GUID attribute for PMXML, XER files and Primavera database.

* Avoid NPE when reading MPP14 custom properties.
* Ensure calculated task attributes are present in JSON output.
* Handle MSPDI files written by German versions of Microsoft Project (based on a contribution by Lord Helmchen)
* Fixed [Issue 277](https://sourceforge.net/p/mpxj/bugs/277): synchronizeTaskIDToHierarchy clears list of tasks
* Fixed [Issue 273](https://sourceforge.net/p/mpxj/bugs/273): PrimaveraPMFileWriter throws Exception at write(..)
* Fixed [Issue 281](https://sourceforge.net/p/mpxj/bugs/281): Parent task is always null when reading a Primavera XER file
* Ensure that Task.getSuccesors() and Task.getPredecessors() return an empty list rather than null.